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Abstract

The North Sea basins comprise a major linked system formed by partial reactivation of the earlier crustal anisotropy. The interaction of Triassic-Jurassic extension with earlier structural trends has resulted in a basin system that variously displays extensional and transfer fault geometry linked geographically to more complex oblique- and strike-slip basin styles. It is therefore important to analyze individual parts of the system with a strict regard to the regional tectonics and to changes in motion of subplates. The successive superposition of Permian-Triassic, Cretaceous, and—to the west of Britain—Tertiary basin growth shows both faulting and subsidence. Regional models can be derived by identifying families of structures that typify the different basic components of the linked system. Many of Thèse structural elements are better understood by a simple shear (Wernicke) detachment model than by a pure shear (McKenzie) detachment model. The linkage to pure or simple shear in the lower crust is not uniquely defined by upper crustal geometry. In some parts of the North Sea, however, deep reflection profiles can be used to suggest a consistent asymmetry in crustal structure.

Linked fault models of basins demonstrate that it may be possible to distinguish upper and lower plate basin margins and composite basin transfer systems on the basis of regional context and local structural styles. Basins that are geographically separated may be mechanically linked at a scale less than that of the lithospheric plates, but of the order of 1000 to 2000 km. Hence, this linkage can be used to predict and model response within the whole basin. The structural evolution of the North Sea and eastern Atlantic margin basins provide a general model for deformation both within plates and on passive margins.

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